Method and apparatus for improving dynamic range in a communication system

Abstract

An apparatus for improving dynamic range includes a frequency down-conversion module that receives an input signal and a bias circuit. The bias circuit includes a first resistor and a second resistor. The first resistor has a first terminal coupled to a bias point and a second terminal coupled to a first voltage reference. The second resistor has a first terminal coupled to the bias point and a second terminal coupled to a second voltage reference. The bias point is coupled to the input signal. The frequency down-conversion module outputs a down-converted output signal. The bias circuit thereby adjusts a voltage of the input signal.

What is claimed is: 
     
       1. An apparatus for improving dynamic range, comprising:
 a frequency down-conversion module that receives an input signal; and 
 a bias circuit comprising:
 a first resistor with a first terminal coupled to a bias point and a second terminal coupled to a first voltage reference; and 
 a second resistor with a first terminal coupled to said bias point and a second terminal coupled to a second voltage reference; 
 
 wherein said bias point is coupled to said input signal; 
 wherein said frequency down-conversion module comprises a switch and a storage element; 
 wherein the switch transfers energy from the input signal to the storage element by non-impulse under-sampling the input signal according to non-impulse pulses of a control signal; 
 wherein an output signal is generated by integrating the transferred energy; 
 wherein the bias point is configured to bias the input signal to have a center voltage that varies within a minimum and a maximum of a voltage range of the control signal; and 
 wherein said frequency down-conversion module outputs a down-converted output signal. 
 
     
     
       2. The apparatus of  claim 1 , further comprising a tank circuit, wherein said bias point is coupled to said input signal via said tank circuit. 
     
     
       3. The apparatus of  claim 2 , wherein said tank circuit comprises a capacitor and an inductor connected in parallel and coupled between said input signal and said bias point. 
     
     
       4. The apparatus of  claim 1 , wherein said bias circuit further comprises a capacitor, wherein a first terminal of said capacitor is coupled to said bias point, and a second terminal of said capacitor is coupled to a third voltage reference. 
     
     
       5. The apparatus of  claim 4 , wherein said capacitor stabilizes said bias point. 
     
     
       6. The apparatus of  claim 1 , wherein a first node of said storage element is coupled to a node of said switch, and a second node of said storage element is coupled to a reference potential. 
     
     
       7. The apparatus of  claim 6 , wherein said storage element comprises a capacitor. 
     
     
       8. The apparatus of  claim 1 , further comprising an impedance match in series with said input signal. 
     
     
       9. The apparatus of  claim 8 , wherein said impedance match comprises an inductor. 
     
     
       10. The apparatus of  claim 1 , further comprising a control signal generator that outputs said control signal. 
     
     
       11. A method of down-converting an electromagnetic signal and improving dynamic range, comprising:
 (1) applying a bias voltage to an input signal; and 
 (2) frequency down-converting the input signal with a frequency down-conversion module to a down-converted signal; 
 wherein step (2) comprises using a switch to transfer energy from the biased input signal to a storage component by non-impulse under-sampling the input signal according to non-impulse pulses of a control signal; 
 wherein step (2) comprises generating an output signal by integrating the transferred energy; and 
 wherein step (1) comprises producing the biased input signal to have a center voltage that varies within a minimum and a maximum of a voltage range of the control signal. 
 
     
     
       12. The method of  claim 11 , wherein step (1) comprises the step of:
 adjusting the center voltage of the input signal. 
 
     
     
       13. The method of  claim 11 , wherein step (1) comprises the step of:
 (A) coupling the input signal to a center terminal of a resistor divider circuit. 
 
     
     
       14. A method of down-converting an electromagnetic signal and improving dynamic range, comprising:
 (1) applying a bias voltage to an input signal; and 
 (2) frequency down-converting the input signal with a frequency down-conversion module to a down-converted signal by non-impulse under-sampling the input signal according to non-impulse pulses of a control signal to thereby transfer energy from the input signal, and integrating the transferred energy; 
 wherein step (1) comprises:
 (A) coupling the input signal to a center terminal of a resistor divider circuit, wherein step (A) comprises:
 (i) using a tank circuit to couple the input signal to the center terminal of the resistor divider circuit. 
 
 
 
     
     
       15. A method of down-converting an input signal, comprising the steps of:
 (1) receiving an input signal; 
 (2) biasing the input signal with a bias voltage to produce a biased input signal; and 
 (3) down-converting the biased input signal to a down-converted signal using a frequency down-conversion module; 
 wherein step (3) comprises transferring energy from the biased input signal by non-impulse under-sampling the input signal according to non-impulse pulses of a control signal; 
 wherein step (3) further comprises integrating the transferred energy thereby generating the down-converted signal; and 
 wherein step (2) comprises producing the biased input signal to have a center voltage that varies within a minimum and a maximum of a voltage range of the control signal. 
 
     
     
       16. The method of  claim 15 , wherein step (1) further comprises receiving a radio frequency (RF) signal. 
     
     
       17. The method of  claim 15 , wherein step (1) further comprises receiving the input signal through an impedance match. 
     
     
       18. The method of  claim 17 , wherein step (1) further comprises receiving the input signal through an inductor. 
     
     
       19. The method of  claim 15 , wherein step (2) further comprises generating the bias voltage using a voltage divider circuit. 
     
     
       20. The method of  claim 19 , wherein step (2) further comprises receiving the bias voltage from the voltage divider circuit. 
     
     
       21. The method of  claim 20 , wherein step (2) further comprises receiving the bias voltage from the voltage divider circuit via a tank circuit. 
     
     
       22. The method of  claim 15 , wherein step (2) further comprises ensuring the center voltage is maintained substantially equal to a midpoint of the voltage range.